A really cute song about cellular respiration to the tune of “I Gotta Feeling” by the Black Eyed Peas.
Today we did a skit in class as an overview of the light reactions of photosynthesis. Here’s basically how it worked:
I had several students stand around one lab table, wearing name tags such as chlorophyll (there were a few of these), xanthophyll, and chlorophyll a. Each had a small plastic ball (like a ping pong ball, but any small spherical object would do). One person stood at the next lab table wearing a nametag labeled “Light”. They were told to shine the light (flashlight) on one of the chlorophyll molecules. The person who was hit by the light then had to raise their “electron” and jump around very excitedly (“excited” electrons). They bumped into the chlorophyll next to them, getting them excited, and then that student bumped into the next one…and so on until the last one excited was chlorophyll a.
Then we had a villain (the primary electron acceptor) come and forcibly steal the electron away from chlorophyll a. This, of course, made chlorophyll a very sad. But luckily, our hero (water) came quickly to the rescue, giving up an electron to chlorophyll a (who became happy again). This, of course, meant that water “died” and flew off as an oxygen “angel” (they flipped their nametag over, changing it from H2O to O2).
Meanwhile, the villain had given the electron it stole to an electron carrier (standing in a straight line along the wall with the following students), who passed it on to the next electron carrier, and the next, until eventually NADP+ got it (flipping their nametag over to NADPH) and walked off into the distance to become part of the Calvin cycle. One student in this same line also represented ATP Synthase; they flipped over the nametag of the person standing next to them from ADP to ATP, and this person also went off with NADPH to be used in the Calvin cycle.
Phew! Of course, I had to talk through it a few times until they could do it on their own, but we had a lot of fun.
At my previous workplace, we typically devoted about 2 days to cellular respiration and photosynthesis in our freshman biology classes.
Yes, biologists, you read that correctly. Two days.
Clearly, these topics are much more complex than 2 days worth of material. Are they enough for 3 weeks, though, in a high school biology 1 class?
This is what I’ve been struggling with over the past week and a half. Since I’ve never taught this material in more detail than two days worth, it’s been challenging to recall some of the information I haven’t had to think about since I was in college. Even the textbook we use (Biology: Exploring Life), which I really like, seems a little too detailed over this particular unit.
I think I’ve managed, though, to get it narrowed down to where I want it. Here’s what we covered for cellular respiration (we haven’t finished photosynthesis yet, so more on that later):
- The overall equation for cellular respiration (and recognizing that the reactants in cellular respiration are the products in photosynthesis, and vice versa)
- Glycolysis summary
- Krebs Cycle summary
- Electron Transport Chain and ATP Synthase summary
Here’s how we summarized each stage:
- takes place in cytoplasm
- splits glucose in half, forming 2 pyruvic acid molecules—-these go into the Krebs Cycle
- also forms 2 NADH (we had to discuss what an electron carrier was, of course)—-these go to the ETC
- net gain of 2 ATP
- takes place in matrix of mitochondria
- “strips off” carbons from the pyruvic acids, which become part of CO2 molecules
- forms many more electron carriers (NADH and FADH2)—-go to the ETC
- gain 2 more ATP
ETC and ATP Synthase–
- found on the inner membrane of the mitochondria
- electron carriers (NADH and FADH2) give up their electrons to the ETC, creating a H+ gradient
- gradient powers the enzyme ATP Synthase, making 34 ATP
- oxygen accepts the electrons and hydrogen from the electron carriers, forming H2O
We didn’t name all of the other enzymes involved, and we didn’t really mention acetyl coA (even though it was in the textbook). It’s not perfect, but I think it makes a decent mix between only 2 days of coverage versus college-level detail. We also discussed fermentation (what happens when there is little/no oxygen present), and I stressed the fact that plants, too, do cellular respiration (some students get confused and think that autotrophs do photosynthesis, making glucose, and therefore they don’t need to do respiration–they fail to see that the glucose still needs to be broken down to make ATP).
We also did a little dance with hand motions. I’ll need to get the exact words later.
What do you do to cover this particular topic?
Heads up, biology teachers. A new chlorophyll has been discovered. Here is some great new stuff to mention when you get to your photosynthesis unit. This newly discovered chlorophyll has been dubbed “chlorophyll f” and apparently can harness light from beyond the red end of the spectrum. Aside from simply being a cool new discovery, it also gives you the opportunity to talk about stromatolites, and who doesn’t enjoy that? 🙂
Read more here: New Chlorophyll Discovered